This invention relates broadly to the art of electrostatographic printing machines, and more particularly to apparatus for extinguishing fires originating in fusing devices thereof.
In many electrostatographic printing machines, copy sheets having toner powder images thereon are conveyed through fusing devices for fusing the images to the copy sheets. The fusing devices, or fusers, generate sufficient heat to permanently fix the heat sensitive toner particles to the copy sheets.
It sometimes inadvertently occurs that the temperatures created by the fusers exceed the kindling temperatures of the copy sheets and thereby cause fires. Such fires, if not quickly extinguished, could spread and thereby result in great damage to the printing machines requiring expensive repair.
Petents which describe sensors for sensing the likelihood or presence of such fires include U.S. Pat. Nos. 3,705,289 to Szostak et al, 3,748,088 to Mooney et al, and 3,804,516 to Mott. Further, U.S. Pat. No. 3,778,222 to Suzuki describes a device to be used with an electrostatographic printer wherein, when a fire is detected in a fuser the ends of the fuser are shut to prevent the spread of this fire beyond the fuser. However, these devices do not appear to extinguish the fires, which would be desirable. Thus, it is an object of this invention to provide a fire extinguishing apparatus for an electrostatographic photocopy machine which effectively extinguishes fires caused by fusers.
It has been suggested to employ a fire wiper-snuffer downstream of a fuser which includes a broad, flat spring to wipe across the tops of copy sheets as they exit from the fuser. However, it has been found that such a device provides undue loading of light-weight copy sheets causing them to buckle and thereby jam in the machine.
A snuffer system is disclosed in U.S. Pat. No. 1,845,840 to Holman for extinguishing fires on a film in a motion picture projector. In this case, the film is pulled between plates which are separated a distance of 1/16 of an inch. The fires are choked for lack of oxygen within the confined space between the plates and the metallic plates reduce the temperature of a flame below the ignition temperature of the film. Although this system may be effective where film is pulled through a gap, it would not appear to work well for copying machines. Such a small gap would load copy sheets to such an extent that many of them would buckle and jam the machine. Also, it would be difficult to guide the leading edges of copy sheets into Holman's gap. Thus, it is yet another object of this invention to provide an effective fire snuffer for an electrostatographic copying machine which does not unduly impede the flow of individual copy sheets.